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Alan E Brain <[log in to unmask]>
Fri, 8 Feb 2002 11:25:11 +1100
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> > Ah, the luxury of having the bandwidth to upload the entire code set
> > :).

A whopping 4k Bits per sec for 15 mins a day. OK, so it takes a week, perhaps 2 if there's lots of telecommands to process.

> "Patchability" can become a driving factor in the software design and
> tool selection
> Changes to data structures present the biggest problem when patching
> flight software.  Ada provides a lot of options (access functions,
> reserving space with 'Size rep clause, etc.), but the safest approach
> seems to be uploading a new flight image (which may require multiple
> orbits).

Multiple orbits is right. Several hundred if the bird's in Sun-synchronous orbit and you only have 1 ground station. It's only in view one orbit in 13, and only for 10-20 mins. Agree that even with these constraints, upload of whole images is the way to go. KISS. Otherwise if anything goes wrong, the program could be in an indeterminate state, and just determining the configuration to recover from on error would be an interesting task.

"In space, no-one can press CTRL-ALT-DEL"